Data-wiping — securely overwriting deleted files with random ones and zeros — makes deleted data much harder to recover. But is it worth the hassle?In most cases, the answer is no. There are much simpler methods for making sure deleted files are truly gone.

Defragging overwrites the areas that the defragged data was moved to, but the new vacant blocks/clusters still contain data. A defrag leaves data in the now free space where the data was before the defrag, or where data was moved temporarily while making enough free contiguous space to defrag a file.

Have you ever watched a defragger in operation, including the map of disk free and occupied blocks before and after the defrag?

If a copy of “live” data is on the system, data wiping won’t help. Instead you should be thinking about physical security of the machine, strong passwords, securing network access, and encryption. It would easy for a data thief to remove the hard drive. If the data is not encrypted then the thief could harvest the data at his leisure, or make a clone copy and return the disk, which would make it very difficult to suspect or detect the theft. (I once had a computer that will tell you that the case has been opened during BIOS POST, but haven’t seen this feature for a long time.)

If the system is being retired or transferred to another entity (donated, sold, recycled, etc.) then it might make sense to do a wipe.

Data wiping consists of overwriting disk blocks with one or multiple patterns. http://en.wikipedia.org/wiki/Data_remanence: according to the 2006 NIST Special Publication 800-88 (p. 7): "Studies have shown that most of today’s media can be effectively cleared by one overwrite" and "for ATA disk drives manufactured after 2001 (over 15 GB) the terms clearing and purging have converged." An analysis by Wright et al. of recovery techniques, including magnetic force microscopy, also concludes that a single wipe is all that is required for modern drives. They point out that the long time required for multiple wipes "has created a situation where many organizations [sic] ignore the issue all together – resulting in data leaks and loss.”

If the drive ever held government data, the contract may specify disposal requirements or one of the government standards may apply.

There were about 7 different government standards for data destruction when I worked on a project with secure erase requirements a few years ago on an aircraft system that would hold classified data. We chose a solid state disk drive that supported several MIL STD secure erase command sequences, including one appropriate for the system. (The vendor even included a mode that would electronically destroy the storage chips.) Once the drive was told to secure erase, it went offline and would no longer respond until the secure erase finished. Even power cycling would not interrupt the offline secure erase.

re: Networking via your electrical wiring
Will the power line networking adapters work across split phase wiring?
For example to use X-10 you need a special device for the signal to reach the other circuits.

re: Networking via your electrical wiring
Will the power line networking adapters work across split phase wiring?
For example to use X-10 you need a special device for the signal to reach the other circuits.

I asked a very similar question to the support staff at Actiontec regarding AC hum and working across different circuits and got this response:

"Negative. Those issues exist with all power line adapters as they are using the home wiring as a substitue [sic] for network cable.
The breaker in your home is not a network device, it will never be capable of sending an IP address from one circuit to the other circuit."

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Deadeye81

"We make a living by what we get, we make a life by what we give." Sir Winston Churchill

I asked a very similar question to the support staff at Actiontec regarding AC hum and working across different circuits and got this response:

"Negative. Those issues exist with all power line adapters as they are using the home wiring as a substitue [sic] for network cable.
The breaker in your home is not a network device, it will never be capable of sending an IP address from one circuit to the other circuit."

I hope Fred's equipment is all on the same circuit.

What a load of nonsense. Your breaker is a bit of wire and it does NOT stop the powerline signal.

I was saddened to see Fred mention powerline adaptors. There are HUGE EMC interference problems with these, as a quick web search will reveal. Existing ones block out shortwave reception and the newer Gigabit types threaten to do the same with normal VHF FM reception. Power wiring is unbalanced and not designed to transmit RF signals, being effectively a big aerial. More information at http://www.mds975.co.uk/Content/amat...erference.html and http://www.ukqrm.org/